Tight linkage of genes that encode the two glutamate synthase subunits of Escherichia coli K-12.

A hybrid deoxyribonucleic acid molecule, plasmid pRSP20, which was isolated from the Clarke and Carbon Escherichia coli gene bank, was shown to complement the gltB31 mutation, which affects the synthesis of glutamate synthase in E. coli strain PA340. We present evidence which demonstrates that plasmid pRSP20 carries an 8-megadalton E. coli chromosomal fragment, including the genes encoding the two unequal glutamate synthase subunits. Polypeptides with molecular weights of about 135,000 and 53,000, which comigrated with purified E. coli glutamate synthase subunit polypeptides and immunoprecipitated with antibodies to E. coli glutamate synthase, were synthesized by minicells carrying the pRSP20 plasmid.